Online marketplaces frequently maintain inventories of items in one or more storage or distribution facilities, which are sometimes called fulfillment centers. Such facilities may include stations for receiving shipments of items, stations for storing such items, and/or stations for preparing such items for delivery to customers. For example, when a vendor delivers an inbound shipment of items to a fulfillment center, the shipment may arrive at a receiving station, where the items included in the shipment may be removed from the containers in which they arrived and transported to one or more storage areas within the fulfillment center. Likewise, when an online marketplace receives an order for one or more items from a customer, the items may be retrieved from their respective storage areas within the fulfillment center and transported to a distribution station, where the items may be prepared for delivery to the customer in an appropriate container with a suitable amount or type of dunnage.
Because modern online marketplaces have the capacity to offer large numbers of unique items for sale to customers, hundreds or even thousands of items may be in motion at any given time within a fulfillment center associated with an online marketplace. Such items may be transported by one or more conveying systems, which are mechanical systems including one or more movers for moving large objects or materials from one location to another that may be employed in a variety of throughput applications. For example, items may be transported throughout a fulfillment center on a conveyor belt, e.g., a system of two or more pulleys or pulley-like wheels causing motion of a continuous loop band that may also include machines or features for changing a direction of travel of objects being conveyed, or for moving objects from one conveyor to another, which are sometimes called diverters or divert mechanisms. Items are typically transported between a receiving station and a storage area, or between the storage area and a distribution station, or to or from any origin or destination within the fulfillment center.
In order to improve the efficiency of fulfillment center operations, it is advantageous to identify an item, or to determine information regarding the item (e.g., characteristics, contents or dimensions of the item) as early as possible. Once an identity of an item, or information regarding the item, has been determined, an appropriate destination for the item may be selected as soon as is practical. For example, the dimensions of an item that has arrived in an inbound shipment must be determined in order to choose an appropriate storage area or region for the item, while the dimensions of an ordered item must be identified in order to select an appropriately sized container for the item. Presently, some systems and methods for determining dimensions of items operate using multiple acoustic sensors that may be oriented with regard to one or more coordinate axes. Such systems may bounce a plurality of sound waves off of surfaces of an item either in series or in parallel, and information regarding the dimensions of the items may be determined from the acoustic properties of the waves reflected from the item's surfaces.
While some acoustic systems may be accurate and effective for determining dimensions of uniformly shaped items or items having substantially constantly shaped faces (e.g., items shaped in the form of cubes or other rectangular solids), such systems may be inaccurate or ineffective where the items to be evaluated are eccentrically shaped (i.e., not uniformly or substantially constantly shaped). Based on empirical data, in some situations, dimensions of eccentrically shaped items that are determined by acoustic means may be off by one-half of an inch or more. Because the offerings of items at online marketplaces continue to grow and diversify over time, the number of eccentrically shaped items that are distributed to customers through fulfillment centers have steadily increased, compounding the effects of the inability to accurately determine dimensions of such items, thereby leading to inefficient uses of space within fulfillment centers and increased shipping costs.